Microelectromechanical (MEMS) devices have found many applications in basic signal transductions. For example, MEMS-based spatial light modulators are transducers that modulate incident light in a spatial pattern in response to optical or electrical inputs. The incident light may be modulated in phase, intensity, polarization, or direction. This modulation may be accomplished through the use of a variety of materials exhibiting magneto-optic, electro-optic, or elastic properties. Such spatial light modulators have many applications, including optical information processing, display systems, and electrostatic printing.
A micromirror-based spatial light modulator is a spatial light modulator consists of an array of micromirrors. The mirror plates are individually addressable and deflectable with electrostatic fields so as to modulate incident light. A typical micromirror device comprises a deformable reflective mirror plate held by a deformable hinge such that the mirror plate can rotate to different positions in response to driving forces, such as electrostatic field. According to the different rotation positions, operation states, such as ON and OFF states in a binary operation mode are defined. In the ON state, incident light is reflected so as to produce a “bright” pixel on a display target, and in the OFF state, incident light is reflected to produce a “dark” pixel on the display target. In an application of displaying an image represented by image pixels having “bright” and “dark” values, the micromirrors are associated with the image pixels, and the micromirrors are individually set to the ON or OFF states according to the “bright” or “dark” values of the image pixels associated with micromirrors. The collective effect of the reflection from the micromirrors at the ON and OFF states for a given incident light is reproduction of the image on the display target. The same operation mechanism is applied to display applications for color images and videos. The color image display is often performed with a color wheel that generates the primary colors or the like. Video display applications are often performed with a sequential color field technique which requires the micromirrors be rotated rapidly and frequently between the ON and OFF state so as to reflect the appropriate “brightness” variation of the image pixels. In either application of image and video display applications, robust electromechanical responses to the driving forces and uniform ON and OFF states of the micromirrors are determinative factors for the evaluations of the product performance and quality.
Therefore, what is desired is a method and apparatus for measuring electromechanical responses of micromirror devices.